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Wai Pong Wong, Yi Zhao and Woon-Puay Koh

The angiotensin-I-converting enzyme (ACE) I/D gene polymorphism has been studied for its role in determining habitual physical activity level, but there is no information from Asian populations. The objective of this study was to determine whether this ACE gene polymorphism was associated with physical activity level among Chinese in Singapore. In this cross-sectional study, 110 normotensive Chinese in Singapore, age 21–61 yr, completed the short-form version of the International Physical Activity Questionnaire and contributed buccal cell samples for genotyping of the ACE I/D gene polymorphism using polymerase chain-reaction amplification. They also provided demographic information and underwent anthropometric measurements. Physical activity level was expressed as continuous (in kcal/wk) and categorical (low, moderate, or high) data. The 3 genotypes of ACE were DD (homozygous for the deletion allele), II (homozygous for the insertion allele), and ID. Among the participants, 28.2% reported low, 49.1% moderate, and 22.7% high physical activity level. Frequencies of the genotypes were 11.8% for DD, 42.7% for ID, and 45.5% for II. ACE genotype was independently associated with physical activity level. After age, gender, and body-mass index were adjusted for, individuals with DD or ID genotypes were more likely to report insufficient or low physical activity level than those with II genotypes (odds ratio = 6.88; 95% confidence interval: 2.26, 20.94). In conclusion, the I/D polymorphism of the ACE gene is significantly associated with self-reported physical activity level in normotensive Chinese Singaporeans.

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Stacy A. Clemes, Beverley M. David, Yi Zhao, Xu Han and Wendy Brown

Background:

In light of evidence linking sedentary behaviors to health outcomes, there have been calls for the measurement of sedentary behavior in surveillance studies. This study examined the convergent validity of 2 self-report measures of sitting time and accelerometer-determined sedentary time (minutes/day of <100 counts/minute).

Methods:

44 adults wore an ActiGraph accelerometer for 7 days, during which they also recorded daily sitting time in a diary, in response to a single-item question. After 7 days, participants completed a new domain-specific questionnaire to assess usual weekday and weekend-day sitting time. Total sitting times recorded from the self-report measures were compared with accelerometer-determined sedentary time.

Results:

Total sitting time calculated from the domain-specific questionnaire did not differ significantly from accelerometer-determined sedentary time on weekdays (mean difference [±SE] = –14 ± 28 mins/day) and weekend days (–4 ± 45 mins/day, both P > .05). Sitting time was significantly underestimated using the single-item specific-day question on weekdays (–173 ± 18 mins/day) and weekend days (–219 ± 23 mins/day, both P < .001).

Conclusions:

When assessed via self-report, the estimation of total sitting time is improved by summing sitting times reported across different domains. The continued improvement of self-report measures of sitting time will be important if we are to further our understanding of the links between sedentary behavior and health.

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Li-Xin Guo, Zhao-Wen Wang, Yi-Min Zhang, Kim-Kheng Lee, Ee-Chon Teo, He Li and Bang-Chun Wen

The aim of this study is to investigate the effect of material property changes in the spinal components on the resonant frequency characteristics of the human spine. Several investigations have reported the material property sensitivity of human spine under static loading conditions, but less research has been devoted to the material property sensitivity of spinal biomechanical characteristics under a vibration environment. A detailed three-dimensional finite element model of the human spine, T12– pelvis, was built and used to predict the influence of material property variation on the resonant frequencies of the human spine. The simulation results reveal that material properties of spinal components have obvious influences on the dynamic characteristics of the spine. The annulus ground substance is the dominant component affecting the vertical resonant frequencies of the spine. The percentage change of the resonant frequency relative to the basic condition was more than 20% if Young’s modulus of disc annulus is less than 1.5 MPa. The vertical resonant frequency may also decrease if Poisson’s ratio of nucleus pulposus of intervertebral disc decreases.